This invention relates to laminated circuit materials. More particularly, this invention relates to fluoropolymeric glass reinforced circuit materials having excellent dimensional stability, electrical properties and a smooth surface. This circuit material is particularly well suited for applications requiring microwave operating frequencies.
Most common printed wiring board materials undergo dimensional changes during processing. These changes are induced by stress relaxation as metal claddings are removed and/or by absorption with processing solutions, and/or by temperature, pressure or humidity excursions. The addition of reinforcing fibers to polymer systems is intended, in part, to reduce the dimensional changes that occur during processing.
With respect to glass reinforced fluoropolymer boards, particularly boards composed of polytetrafluoroethylene (PTFE), there have been three common prior art types.